Technique for detecting twisted motion of electric working machine

Patent metadata

Field	Value
Publication number	US-11607789-B2
Application number	US-202017018079-A
Country	US
Kind code	B2
Filing date	Sep 11, 2020
Priority date	Sep 12, 2019
Publication date	Mar 21, 2023
Grant date	Mar 21, 2023

Abstract

An electric working machine in one aspect of the present disclosure includes an output shaft, a motor, a housing, an acceleration detector, a twisted motion detector, a reference level changer, and a motor controller. The acceleration detector detects an acceleration of the housing in a circumferential direction of the output shaft. The twisted motion detector detects a twisted motion of the housing based on a reference level and the acceleration detected. The reference level determines that the housing is twisted. The reference level changer changes the reference level based on a rotating motion of the output shaft.

First claim

What is claimed is:

1. An electric working machine comprising:
an output shaft configured to be attached to a tool bit;
a motor configured to generate a drive force to rotate the output shaft in a circumferential direction of the output shaft;
a housing that houses the output shaft and the motor, the housing being configured to be gripped by a user of the electric working machine;
an acceleration detector configured to detect an acceleration imposed on the housing in the circumferential direction;
a twisted motion detector configured to detect a twisted motion of the housing based on a reference level and the acceleration detected by the acceleration detector, the reference level determining that the housing is twisted; and
a processor configured to:
change the reference level based on a manual operation from the user;
receive a drive command;
control the motor in accordance with the drive command; and
stop or restrain drive of the motor in response to the twisted motion detector detecting the twisted motion.

2. The electric working machine according to claim 1 , further comprising:
a manual switch configured to receive the manual operation from the user,
wherein the processor is configured to change the reference level in accordance with the manual operation received by the manual switch.

3. An electric working machine comprising:
an output shaft configured to be attached to a tool bit;
a motor configured to generate a drive force to rotate the output shaft in a circumferential direction of the output shaft;
a housing that houses the output shaft and the motor, the housing being configured to be gripped by a user of the electric working machine;
an acceleration detector configured to detect an acceleration imposed on the housing in the circumferential direction;
a twisted motion detector configured to detect a twisted motion of the housing based on a reference level and the acceleration detected by the acceleration detector, the reference level determining that the housing is twisted;
a manual switch configured to receive a manual operation from the user, the manual switch being further configured to define a rotating motion of the output shaft based on the manual operation received by the manual switch, the reference level being changed in accordance with the manual operation received by the manual switch; and
a motor control circuit configured to:
receive a drive command;
control the motor in accordance with the drive command; and
stop or restrain drive of the motor in response to the twisted motion detector detecting the twisted motion.

4. The electric working machine according to claim 3 , further comprising:
a transmission housed in the housing, the transmission having a first gear ratio and a second gear ratio, the transmission being configured to be switched to either the first gear ratio or the second gear ratio, the transmission being configured to transmit the drive force to the output shaft while changing a rotational speed of the motor via the first gear ratio or the second gear ratio, and the first gear ratio being higher than the second gear ratio,
wherein the manual switch includes a gear ratio selector configured to select either the first gear ratio or the second gear ratio in accordance with the manual operation received by the manual switch, and
the reference level is changed in response to the first gear ratio or the second gear ratio being selected by the gear ratio selector.

5. The electric working machine according to claim 3 ,
wherein the manual switch includes a drive command transmitter configured to transmit the drive command in accordance with the manual operation received by the manual switch,
the drive command varies in accordance with details of the manual operation, and
the reference level is changed in accordance with the drive command transmitted from the drive command transmitter.

6. The electric working machine according to claim 3 ,
wherein the manual switch includes an upper limit speed setter configured to set an upper limit rotational speed in accordance with the manual operation received by the manual switch,
the motor control circuit is configured to limit a rotational speed of the motor or a rotational speed of the output shaft to the upper limit rotational speed that is set by the upper limit speed setter or less, and
the reference level is changed in accordance with the upper limit rotational speed that is set by the upper limit speed setter.

7. The electric working machine according to claim 3 ,
wherein the manual switch includes an upper limit torque setter configured to set an upper limit of an output torque generated by the output shaft in accordance with the manual operation received by the manual switch,
the motor control circuit is configured to stop the drive of the motor in response to the output torque reaching the upper limit that is set by the upper limit torque setter, and
the reference level is changed in accordance with the upper limit that is set by the upper limit torque setter.

8. The electric working machine according to claim 3 ,
wherein the acceleration detector is configured to transmit a detection signal that indicates the acceleration detected by the acceleration detector,
the twisted motion detector includes an electronic filter having a cutoff frequency, the electronic filter being configured to extract a detection value from the detection signal, the cutoff frequency being higher than a low frequency band and being changeable, and the detection value indicating the acceleration detected,
the twisted motion detector is configured to detect the twisted motion based on the reference level and the detection value, and
the cutoff frequency is changed as the reference level.

9. The electric working machine according to claim 8 ,
wherein the cutoff frequency is lowered in accordance with a decrease in a rotational speed of the output shaft.

10. The electric working machine according to claim 3 ,
wherein the acceleration detector is configured to transmit a detection signal that indicates the acceleration detected by the acceleration detector,
the twisted motion detector is configured to perform a signal processing on the detection signal to thereby obtain a feature value of the acceleration,
the twisted motion detector is configured to detect the twisted motion in response to the feature value exceeding a threshold, and
the threshold is changed as the reference level.

11. The electric working machine according to claim 10 ,
wherein the threshold is lowered in response to a rotational speed of the output shaft decreasing in accordance with the manual operation received by the manual switch.

12. The electric working machine according to claim 3 ,
wherein the reference level is manually set by the user in association with details of the manual operation.

13. The electric working machine according to claim 3 ,
wherein the manual switch includes a rotation direction setter configured to set a rotation direction of the motor to either a first direction or a second direction in accordance with the manual operation received by the manual switch,
the motor control circuit is configured to control the motor such that the motor rotates in the rotation direction that is set by the rotation direction setter, and
the reference level is changed in accordance with the rotation direction that is set by the rotation direction setter.

14. The electric working machine according to claim 13 ,
wherein the acceleration detector is configured to transmit a detection signal that indicates the acceleration detected by

Assignees

• Makita Corp

Inventors

• Sunabe Hikaru
• Yamamoto Hirokatsu
• Osada Takaaki

Classifications

• B25D2250/205

  for torque · CPC title

• H02P23/04

  specially adapted for damping motor oscillations, e.g. for reducing hunting · CPC title

• H02K7/14

  Structural association with mechanical loads, e.g. with hand-held machine tools or fans (with fan or impeller for cooling the machine H02K9/06) · CPC title

• B25F5/001 Primary

  Gearings, speed selectors, clutches or the like specially adapted for rotary tools · CPC title

• B25D16/006

  Mode changers; Mechanisms connected thereto · CPC title